JPH0546991B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application] The present invention relates to a method for manufacturing an integrated amorphous silicon thin film solar cell. More specifically, a plurality of partitioned metal electrode layers stacked on the same substrate,
The present invention relates to a method for manufacturing an integrated solar cell in which a cell consisting of an amorphous silicon layer and a transparent electrode layer is connected by laser beam irradiation. [Prior art] Amorphous silicon semiconductor films can be deposited uniformly over a wide area at low substrate temperatures by glow discharge decomposition using silane gas, etc., and can be deposited on various substrates such as glass, polymer films, ceramic plates, metal foils, etc. Because the substrate can be selected, it is widely studied as a semiconductor film for solar cells. The basic structure of an amorphous silicon solar cell is a laminated structure of metal electrode layer/amorphous silicon semiconductor layer/transparent electrode layer provided on the various substrates mentioned above. Utilizing the characteristics of amorphous silicon layer deposition, JP-A-59
A large area where a metal electrode layer is provided using the roll-to-roll method disclosed in Publication No. 34668 or the three-chamber separation formation method published in Japan Journal of Applied Physics, Vol. 21, No. 3, page 413 (1982). It is easy to deposit an amorphous silicon layer on a long substrate. Further, it is also easy to provide the transparent electrode layer of the other current extraction electrode over a large area. However, in order for the above-mentioned laminate to function as a solar cell, it is necessary to attach lead terminals to the metal electrode layer and the transparent electrode layer. Furthermore, in order to obtain an output voltage of several tens of V or more, which is necessary for practical use, the solar cell provided on the large-area substrate must be divided using a laser scribing method, etc., and then the adjacent metal electrode layer and transparent electrode layer must be separated. It is necessary to connect them in series. In such a case, a method is usually used in which the lowest metal electrode layer is exposed and then connected to the adjacent upper electrode layer or lead extraction electrode. Methods for exposing this metal electrode layer include: using a metal mask when depositing the amorphous silicon layer; removing the silicon layer using wet or dry etching after depositing the amorphous silicon layer; A method has been used in which after layer deposition, only the silicon layer is selectively melted and evaporated by laser irradiation to remove it. Among these methods, the method is not only unsuitable for long, large-area roll-to-roll methods, but also for the three-chamber separation method, thermal expansion of the substrate and mask occurs during the heating process during amorphous silicon deposition. Due to the deterioration of adhesion due to the difference in ratio, the amorphous silicon component wraps around, making it difficult to obtain a good pattern and making it difficult to expose the electrically good surface of the metal layer. Although this method is possible by combining resist coating and etching, it requires many steps such as resist coating, exposure, cleaning, and etching, and is not suitable for manufacturing solar cells in large quantities at low cost. In the other method, the high temperature required to melt the silicon layer causes damage to the metal electrode layer using a high-melting point metal, making it impossible to expose the electrically good metal layer surface. The reality is that it is not possible to selectively remove only the silicon layer with low melting point metals such as metals. In contrast, as disclosed in Japanese Patent Application Laid-Open No. 61-214483, the present inventors patterned and provided an insulating resin layer, and then connected in series a plurality of unit cells that were divided by laser beam irradiation. On the occasion of
A highly conductive connection electrode is formed in a predetermined pattern on each unit cell, and a laser beam is irradiated onto the electrode portion to melt the metal electrode layer, the connection electrode, and all the layers between them. We proposed a method for ohmic bonding between layers and connecting electrodes. However, subsequent studies revealed that although a good connection is usually obtained using the above connection method, sometimes the constituent layers melted at the center of the irradiation due to laser beam irradiation evaporate and scatter, making it impossible to obtain a good ohmic connection. It has been found that there are some issues that need to be improved, such as evaporated matter scattering on the cell surface, adversely affecting the cell characteristics, and sometimes causing poor appearance. [Object of the invention] The present invention eliminates the above-mentioned drawbacks and provides a method for bonding a connecting electrode to a metal electrode surface for taking out lead terminals on a large-area substrate or connecting divided solar cells in series. The object of the present invention is to provide an improved and simple method for manufacturing an integrated solar cell. [Structure and operation of the invention] The above-mentioned objects are achieved by the present invention as described below.
That is, the present invention provides a cell comprising a plurality of partitioned metal electrode layers, an amorphous silicon semiconductor layer serving as a photovoltaic layer, and a transparent electrode layer that are stacked on the same substrate, and the connecting portion of the cell is exposed to laser light. In a method for manufacturing an integrated solar cell that is melted and connected using After providing a surface protective layer on the connection part, the connection electrode part is irradiated with laser light to melt the metal electrode layer, the connection electrode, and all the layers between them, and the metal electrode layer and the connection electrode are melted. This is a method for manufacturing an integrated solar cell characterized by ohmic bonding. The above-mentioned present invention was developed as a result of various studies to solve the above-mentioned drawbacks of the conventional method. After providing a surface protective layer on at least the connecting portion of the cell, the connecting electrode portion is irradiated with a laser beam, and a metal electrode layer, When obtaining an ohmic junction by melting part of the amorphous silicon semiconductor layer, transparent electrode layer, and connection electrode, the surface protective layer prevents evaporation and scattering of the melt, resulting in a good appearance. This method was developed based on the discovery that an ohmic junction with low junction resistance could be obtained. As mentioned above, the present invention is very simple and mass-produced using the roll-to-roll method, in which series connection can be obtained by simply irradiating a laser beam in the final cell form in which connection electrodes are formed at connection points and a surface protective layer is provided. This is a legally appropriate method. Furthermore, when the substrate is a light-transmitting substrate and the laser beam is irradiated from the substrate side, the laser beam can be irradiated based on the position of the divided metal electrode layer, which improves the accuracy of the laser beam irradiation position. It was done. Therefore, the width of the connecting electrode can be narrowed, making it possible to expand the effective light incident area as a solar cell. The details of the present invention will be specifically explained below. Although any substrate made of an electrically insulating material can be used as the electrically insulating substrate of the present invention, a light-transmitting substrate is particularly preferably used for the reasons described above. Specifically, polymer films, ceramic plates,
A glass plate or a metal foil layer with an insulating layer on the surface can be used, but it is preferable to use a roll-to-roll method, in which the constituent layers can be deposited one after another on a long moving substrate, making it suitable for mass production. Molecular films are used. The polymer film may be any light-transmitting polymer film that has the heat resistance necessary for amorphous silicon deposition, but preferably polyethylene terephthalate (PET) film or polyethylene naphthalate film, which have excellent mechanical properties. Film, polyether sulfone film, etc. are used. The metal electrode layer provided on the substrate is made of a material with good electrical conductivity such as Al or Ag.
The main ingredients are metals with melting points below 1000℃, including Ti,
Single metals such as W, Pt, Co, Cr, nichrome, and stainless steel, and laminated structure layers with alloy metal thin films are used. Further, these metal electrode layers preferably have a thickness of 0.3 μm or more from the viewpoint of reducing electrical resistance and mechanical strength. The amorphous silicon layer can be formed using any known photovoltaic layer, and is not particularly limited. Specifically, it can be formed using a plasma CVD method using glow discharge decomposition of a known silane gas, disilane gas, etc. There are pin-shaped laminated photovoltaic layers, etc.
The amorphous silicon photovoltaic layer may include not only multilayer tandem structures such as pin/pin/, pin/pin/pin, but also narrow band gap structures such as amorphous silicon germanium and amorphous silicon carbide. Alternatively, a wideband cap semiconductor layer can be used as appropriate. Further, the transparent electrode layer is not particularly limited, and any known material can be used as is, and various metal oxides are preferably used. Specifically, a metal oxide layer such as indium oxide, tin oxide, cadmium stannate, indium oxide, tin, or a laminate of a metal thin film and an oxide dielectric material is applied. Gold, silver, copper, Al,
A layer mainly composed of nickel or an alloy thereof is applied. This connection electrode is patterned and formed on the transparent electrode layer using a physical deposition method such as a vacuum evaporation method or a sputtering method. Note that the thin film at this time preferably has a thickness of 0.5 μm or more. Further, the connecting electrode can also be provided by a chemical method such as plating, and the film thickness in this case is the same as described above. Furthermore, a method of providing a conductive resin using fine powder of gold, silver, copper, Al, nickel, carbon, etc. by screen printing or the like can be applied. This screen printing method is desirable from the viewpoint of continuous productivity. As the thickness of the printed conductive layer
5 μm or more is required for electrical resistance. As the laser light, any light in the wavelength range that can be absorbed by each constituent layer is sufficient, and light with a wavelength of 0.2 μm is used.
Preferably, it is currently widely used industrially.
A YAG laser is used. In order to form an integrated solar cell, it is first necessary to divide each constituent layer into a unit cell, but as disclosed in Japanese Patent Application Laid-Open No. 61-214483, a black insulating resin layer was patterned and provided. This can be done by irradiating and running a laser beam. In order to connect each divided unit cell, the connection electrode layer is formed using the method described above. The surface protective layer provided on the cell to prevent evaporation and scattering of the melt during laser beam irradiation may be made of any material that has heat resistance and does not melt during laser irradiation, such as glass, transparent ceramic plate, resin layer, polymer, etc. Film, etc. can be used. Among them, a polymer film that can be laminated by a roll-to-roll method is preferably used, and a polymer resin layer that can be easily formed by a screen printing method is particularly preferably used from the viewpoint of productivity. Note that when a surface protective layer is provided on the entire surface of the light incident side of the cell, the surface protective layer needs to be transparent. As the polymer film used as the surface protective layer, a film with excellent transparency such as polyethylene terephthalate film, polyethylene naphthalate film, polycarbonate film, etc. is selected, and is provided on the cell surface by a lamination method. At this time, it is also possible to laminate the back side of the cell as a protective layer. For the transparent polymer resin layer, choose from epoxy, phenol, polyester, melamine, polyurethane, polyimide, and other resins, taking into consideration flexibility, moisture resistance, etc., depending on the intended use of the solar cell. A suitable resin is selected. When a resin layer is used, openings for extracting output from the solar cell can be provided in any desired shape, making it possible to further improve productivity. It is clear from its effect that the above-mentioned protective layer should be provided at least on the surface opposite to the cell substrate corresponding to the connection part of the connection electrode, and from the viewpoint of photoelectric conversion efficiency, it is recommended to provide it only on the connection part. Although it is preferable, from the viewpoint of productivity, the output extraction portion may be patterned and provided on the entire surface, and may also be provided on the substrate side using a polymer film or the like so as to serve as a protective layer for sealing. If it is used also as a protective layer for module sealing, it is advantageous in terms of conversion efficiency and productivity. It is selected as appropriate depending on the purpose. The cell provided with the surface protective layer is irradiated with laser light from the back side, etc., and the connecting electrode and the lower metal electrode layer are melted and connected in series. The power during laser beam irradiation depends on the substrate material used in the cell, the metal electrode layer material,
The connection electrode material is experimentally selected depending on the presence or absence of a backside protective layer and its material. Further, the laser beam irradiation position is determined using the scribe grooves that are divided into unit cells by the laser scribing method according to the method described in Japanese Patent Application Laid-Open No. 61-214483. Examples of the present invention will be shown below. [Example 1] FIG. 1 is a cross-sectional view of a module explaining each step of the example, and FIG. 2 is a plan view showing the formation pattern of an insulating layer for forming the module in the example.
FIG. 3 is a plan view showing a pattern of connection electrodes for forming a module in the embodiment. As the polymer film substrate 1, a 100 μm thick polyethylene terephthalate film (PET) was used. First, the film substrate 1 was mounted on a DC magnetron sputtering device, and an aluminum layer (Al) of 0.4 μm and a stainless steel layer (SS) of 100 Å were successively deposited in an Ar atmosphere of 10 ^-3 torr. A layer 2 was provided on a long film substrate 1 (see Figure 1). Further, on this PET/Al/SS laminate, a pin-type amorphous silicon layer 3, which will become a photovoltaic layer, is formed into a long length by the roll-to-roll method disclosed in Japanese Patent Application Laid-Open No. 59-34668. A boron (B)-doped P layer of 300 Å, an i-layer of 0.5 μm, and a phosphorus (P)-doped N layer of 200 Å were deposited over a large area (FIG. 1A). In order to form a solar cell in which three cells C are connected in series on the same substrate, the cell shown in Figure 2 is placed on a stack of PET/Al/SS/amorphous silicon layers with a large area of 10 cm x 10 cm. A black insulating paste was printed using a screen printing method according to the decomposition pattern, and electrical insulating layers 4a and 4b were formed to prevent poor insulation between electrodes around the dividing grooves during dividing process (first
Figure B). Thereafter, a transparent electrode layer 5 made of indium oxide is deposited on top of it by electron beam evaporation.
It was deposited uniformly to a thickness of 600 Å (Fig. 1C). Next, by a laser scribing method using a YAG laser, the parts are divided according to the division pattern shown in Figure 2.
It was divided into three cells C of 3.3 cm x 10 cm as follows. In other words, the YAG laser was adjusted to a Q-switch frequency of 2 KHz, power (peak output) of 1 KW, beam diameter of 100 μm, and scanning speed of 3.2 cm/sec.
Along the electrical insulating layer 4a, a cell dividing groove 6 is formed by evaporating all layers except for the substrate 1 in order to divide the cell C, and along the electrical insulating layer 4b, a YAG laser is used with a peak output of 150 W. Other than that, under the same conditions as above, only the transparent electrode layer 5 was evaporated, and electrode dividing grooves 7 for separating the connecting electrode portions A were formed to divide the cell into cells (FIG. 1D). Next, as shown in FIG. 1E, the cell dividing grooves 6 and electrode dividing grooves 7 formed by laser beam irradiation are filled with electrically insulating resin by screen printing, coating, etc. to form a closing resin layer 8. is formed. As the electrically insulating resin forming the closing resin layer 8, the resins for the electrically insulating layers 4a and 4b described above can be used as they are. Thereafter, silver conductive resin was deposited to a thickness of 13 μm in the following pattern shown in Figure 3 using a screen printing method.
A connection electrode that also served as a collection electrode and a lead extraction electrode were formed (FIG. 1F). That is, the busbar part 10 of the collecting electrode 9 was located on the connecting electrode part A so as to serve as a connecting part, and the finger parts 9 were arranged from the busbar part 10 at predetermined intervals in a direction perpendicular to the busbar part 10 so as to span adjacent cells. It is provided in the pattern. Note that the bus bar portion 10 of the cell C at the right end in FIG. 3 serves as an electrode for lead extraction. The above solar cell was laminated with a 50 μm thick polyester film having excellent light transmittance as a surface protective layer 11 via a transparent adhesive layer 12 to form a structure that protects the outermost surface (FIG. 1G). Thereafter, a YAG laser beam 13 was irradiated from the back surface onto the connecting electrode portion A along the cell dividing groove 6 used for dividing the cells. The laser output at this time is the Q switch frequency
The average output was 3W at 2KHz. This is the conventional method. Photoelectric conversion when three series modules with the same configuration, which were fused and connected by irradiating the connecting electrode part A from the surface with a laser beam before lamination, are laminated with a polyester film protective layer of the same thickness (50 μm) (Comparative Example 1) Compared to the efficiency (EFF), in the module of the present invention (Example 1) whose back side was irradiated with the laser described above, an increase in efficiency was observed due to an increase in the effective area contributing to power generation, as shown in Table 1. . The module characteristics in Table 1 are measured values under a solar simulator with AM=1,100 mW/cm ² .

[Table] [Example 2] A module having the same configuration as Example 1 except for the transparent protective layer, and having four cells connected in series as shown in Fig. 4, was created in the same manner as in Example 1 as follows. . That is, as in Example 1, a 100 μm thick
Al/SS metal electrode layer on PET film substrate, pin
After sequentially depositing the mold amorphous silicon layers, four unit cells C each having a size of 1 cm x 1 cm as shown in FIG.
A black electrical insulating layer 4 with a pattern of connecting pieces in series.
a and 4b were printed. Thereafter, a transparent electrode layer consisting of an indium oxide layer was deposited in a vacuum in the same manner as in Example 1, and then the cell was divided into unit cells C by scanning the electric insulating layers 4a and 4b with a YAG laser beam. . Note that the laser beam scanning conditions and the like are also the same as in Example 1. Connection electrodes for connecting four unit cells in series are made of black carbon conductive resin in the pattern shown in FIG. A pattern having finger portions 9 extending over the top was formed by screen printing. The thickness of the carbon conductive resin layer was 20 μm. Next, a surface protective layer 11 was formed using a transparent polymer resin layer in the following manner. The transparent polymer resin layer was formed using a phenolic resin to a thickness of 15 μm by screen printing. At this time, by patterning the phenol resin layer as shown in FIG. 4C and printing with openings 11a for lead electrodes, it was possible to easily take out lead electrodes from both ends of the module after series connection. Thereafter, a YAG laser beam was irradiated from the back side with a Q-switch frequency of 2KHz and an average output of 3W. As shown in Table 2, an increase in efficiency was observed due to an increase in the effective area contributing to expression, and a module (Example 2) with good appearance was obtained. Table 2 shows, as Comparative Example 2, the measurement results of a module with the same structure that was similarly fused and connected with a laser beam without a surface protective layer, and then provided with the same protective layer as the surface protective layer of Example 2. . The characteristics in Table 2 are the results of measurements under a 200 lux white fluorescent lamp.

[Table] [Example 3] The connection resistance at the series connection portion of a solar cell having the same configuration as Example 1 and using a PET film as a substrate was measured. A black electric insulating layer was provided on the PET/Al/SS/amorphous silicon layer laminate obtained in Example 1 as in Example 1, and a transparent electrode layer made of an ITO layer was deposited and then irradiated with laser light. The cell was divided into parts. After printing silver conductive resin as a connection electrode, 50μm PET film is laminated as a surface protection layer, and the average laser output is 3W and Q switch frequency is 2KHz from the back side.
They were then irradiated and melted to make a series connection.

[Brief explanation of the drawing]

1A to 1G are side sectional views showing the structure of the module of Example 1 and the process of its formation, and FIG. 1F
3 is a partial side sectional view taken along the line A-B in FIG. 3, FIG. 2 is a plan view illustrating the electrical insulating layer formation pattern for forming a module in Example 1, and FIG. 3 is a partial side sectional view taken along line A-B in FIG.
FIGS. 4A to 4C are plan views showing patterns of the collecting electrode and connection electrode of the module of Example 2, and FIGS.
FIG. 3 is a plan view showing formation patterns of respective surface protective layers. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Metal electrode layer, 3... Amorphous silicon layer, 4a, 4b... Electrical insulating layer, 5...
Transparent electrode layer, 6... Cell dividing groove, 7... Electrode dividing groove, 8... Closing resin layer, 9... Collection electrode section, 10
... Busbar part, 11 ... Surface protective layer, 12 ...
Adhesive layer.

Claims (1)

[Scope of Claims] 1 A cell consisting of a plurality of partitioned metal electrode layers, an amorphous silicon layer serving as a photovoltaic layer, and a transparent electrode layer stacked on the same substrate is exposed to a laser beam at the connection portion of the cell. In a method for manufacturing an integrated solar cell that is melted and connected using After providing a surface protective layer on the connection part, the connection part is irradiated with laser light to melt the metal electrode layer, the connection electrode, and all the layers between them, and ohmic-bond the metal electrode layer and the connection electrode. A method for manufacturing an integrated solar cell, characterized by: 2. The method of manufacturing an integrated solar cell according to claim 1, wherein the substrate is a light-transmitting substrate, and the laser beam irradiation is performed from the substrate surface toward the connecting electrode portion. 3. A method for manufacturing an integrated solar cell according to claim 1 or 2, wherein a transparent surface protective layer is laminated over substantially the entire surface of the cell. 4. The method for manufacturing an integrated solar cell according to any one of claims 1 to 3, wherein the surface protective layer is a polymer resin layer provided by a screen printing method. 5. Claim 4, wherein the polymer resin surface protective layer provided by the screen printing method is formed in a pattern having openings for taking out the output of the solar cell.
A method for manufacturing an integrated solar cell as described in Section 1. 6. The method for manufacturing an integrated solar cell according to any one of claims 1 to 5, wherein the substrate is a long polymer film.